sip trunking: deployment considerations at the trunking: deployment considerations at the ......

Download SIP Trunking: Deployment Considerations at the   Trunking: Deployment Considerations at the ... Deployment Considerations at the Network Edge ... A SIP trunk is primarily implemented as a set of concurrent

Post on 08-Mar-2018

213 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • SIP Trunking: Deployment Considerations at the Network Edge

    Small Logo

    Medium Logo

    Large Logo

    White Paper

  • Executive SummaryThe move to Voice over IP (VoIP) and Fax over IP (FoIP) in the enterprise has, until relatively recently, been focused on

    communication within the private enterprise network. Now, some enterprises are using SIP trunks provided by Internet

    Telephony Service Providers (ITSPs) to connect their internal networks to external, public IP networks. SIP trunking is

    one of the first steps in an enterprises PSTN to VoIP transition, and it enjoys broad availability from service providers

    in many regions, including many incumbent PSTN service providers.

    Adopting a SIP trunking service is not a simple process. In fact, many enterprises need support and guidance as

    they move to SIP trunking. Enterprises need a way to connect their existing voice infrastructure to SIP trunks without

    making major changes to their existing voice or data infrastructures. In addition, to provide the necessary protections

    for the enterprise, there needs to be a mechanism for implementing Network Address Translation (NAT) and firewall

    traversal, SIP interoperability, and network edge security; as well as a mechanism for providing a clear demarcation

    point or boundary for real-time IP communication services at the enterprise edge between the external and internal

    IP networks.

    This paper provides an overview of SIP trunking and the benefits it can bring to the enterprise. It also provides

    information about how to address issues at the enterprise network edge when deploying a SIP trunking service.

    White PaperSIP Trunking: Deployment Considerations at the Network Edge

  • White PaperSIP Trunking: Deployment Considerations at the Network Edge

    Table of ContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    Significant Cost Savings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    Increased Provisioning Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    SIP Trunking Challenges for the Enterprise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    Network Address Translation and Firewall Traversal Issues. . . . . . . . . . . . . . . . . . . . . . 2

    SIP Interoperability Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    Network Edge Security Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    Network Demarcation Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    Legacy PBX Infrastructure Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

    Fax over IP Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

    Defining and Securing the Enterprise Network Edge for SIP Trunking . . . . . . . . . . . . . . . . . . 5

    Using an Enterprise Border Element to Facilitate a SIP Trunking Service . . . . . . . . . . . . . . . 5

    TDM or Hybrid PBX Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    IP-PBX Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

    Future Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    Unified Communications and Multimedia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    High Definition Voice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    Network Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    Dialogic Products that Provide Border Element Functionality . . . . . . . . . . . . . . . . . . . . . . . . 8

    Dialogic BorderNet 500 Gateways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    Dialogic IMG 1010 Integrated Media Gateway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

    For More Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

    1

  • SIP Trunking: Deployment Considerations at the Network Edge

    White Paper

    2

    Introduction

    SIP Trunking is a real-time IP communications service delivered by an Internet Telephony Service Provider (ITSP) that allows enterprises to route inbound and outbound voice and fax traffic over a broadband data service using the Session Initiation Protocol (SIP), Real-Time Transport Protocol (RTP), and Fax over IP (FoIP) protocol known as T.38. As an access alternative to the traditional Public Switched Telephone Network (PSTN), SIP trunking extends VoIP and FoIP connectivity beyond the enterprise network edge.

    A SIP trunk is primarily implemented as a set of concurrent call sessions routed over the IP backbone of an Internet Service Provider (ISP) by an ITSP. The ISP and ITSP may be one and the same, or an ITSP may leverage third-party ISP IP backbones and enterprise broadband connections to deliver the SIP trunking service. Because SIP trunking enables an enterprise to use the same IP connection for voice, fax, and data communications, it can yield significant cost savings compared to TDM trunking. SIP trunking also offers more provisioning flexibility than TDM trunking.

    Significant Cost Savings

    Most of the installed base of TDM PBXs, hybrid PBXs, and IP-PBXs is provisioned with TDM trunking (T1/E1/PRI, analog, or BRI) for PSTN voice connectivity. At the same time, most enterprise sites have broadband IP connectivity for Internet/WAN services. By moving some or all public network voice and fax traffic from TDM trunks to SIP trunks, the enterprise can remove expensive TDM trunks and leverage its broadband data pipe to run voice service over a cost-reduced SIP trunk.

    Increased Provisioning Flexibility

    With a SIP trunking service, customers can subscribe to concurrent SIP trunking sessions on an as-needed basis instead of subscribing to PSTN services, such as PRI T1/E1, which are typically provisioned in fixed channel increments. In addition, ongoing changes to SIP trunking service provisioning are typically done remotely, eliminating the need to schedule a site visit. This allows customers to more easily add or remove SIP trunking sessions when circumstances change.

    SIP Trunking Challenges for the Enterprise

    There are a number of challenges that need to be addressed in order to support the enterprise in the move to SIP trunking, including:

    Network Address Translation (NAT) and firewall traversal

    SIP interoperability

    Network edge security

    Network demarcation

    Legacy PBX infrastructure

    Fax over IP

    Network Address Translation and Firewall Traversal Issues

    Network Address Translation (NAT) is the technology that translates between the IP addresses in the private enterprise network topology and the public addresses on the Internet. It is often used to maintain an internal network of private addresses and to map them externally to a single public address. NAT is implemented at the routing device or network edge border device.

    SIP is an application layer protocol that sends network addresses and port allocations within the application data, and it may use multiple ports to set up a connection. For instance, SIP as the signaling protocol may use a different network port than the RTP stream that carries the actual media (audio packets that make up the voice communications). NAT, however, resides at the transport layer and does not change the SIP addressing, which makes information received at the remote end invalid.

    SIP Server functionality, combined with SIP Proxy and SIP Registrar functionality, can resolve NAT and port allocation issues by correctly translating IP addresses and port allocations in SIP from private internal addresses and port allocations to public external addresses and port allocations. SIP Server, SIP Proxy, and SIP Registrar can also monitor incoming SIP connections to provide similar address and port translations for incoming SIP calls. This monitoring functionality needs to be in the network edge border device, whether it is a SIP firewall or a SIP-capable edge device.

  • SIP Trunking: Deployment Considerations at the Network Edge

    White Paper

    3

    An alternative for resolving NAT traversal issues is to use the IETF protocols STUN (Simple Traversal of UDP through NATs), TURN (Traversal Using Relay NAT), and ICE (Interactive Connectivity Establishment). These protocols allow the creation of pinholes through the enterprise firewall that allow the SIP signaling and media to pass through. While these approaches provide viable alternatives for addressing NAT issues, they bypass the firewall and run on client and external servers. Keeping NAT translation functionality inside the firewall provides a more secure environment than using STUN, TURN, or ICE for NAT traversal.

    SIP Interoperability Issues

    Different vendors can have subtle differences in their SIP implementations, and there

Recommended

View more >